1. Field of the Invention
The present invention relates to a secondary battery. More specifically, the present invention relates to an electrode assembly and a lithium secondary battery comprising the same.
2. Description of the Related Art
Generally, the lithium secondary battery employs lithium-based oxide as a positive electrode active material and a carbon material as a negative electrode active material. Further, the lithium secondary batteries may be broadly classified into a liquid electrolyte battery and a polymer electrolyte battery, depending on the type of electrolytes used in them. The lithium battery using a liquid electrolyte is known as a lithium ion battery, and the lithium battery using a polymer electrolyte is known as a lithium polymer battery. In addition, the lithium secondary battery may be formed in various shapes, and the typical shape is a cylindrical shape, a polygonal shape or a pouch shape.
An electrode assembly is seated inside a case of such a lithium secondary battery. The electrode assembly is formed by stacking or winding a positive electrode plate, a negative electrode plate and a separator disposed therebetween. An electrode plate including the positive electrode plate and the negative electrode plate is composed of a current collector and an active material layer applied to at least one surface of the current collector. Both ends of the current collector are often provided with non-coating portions which are not coated with the active material layer. An electrode tab is provided on either one of the non-coating portions.
An insulating tape is attached to the boundary between the active material layer and the non-coating portion with formation of the electrode tab. The insulating tape protects an electrical connection part between the electrode plate and the electrode tab and prevents the occurrence of a short circuit due to direct contact between different electrode plates of opposite polarities.
Unfortunately, even though an insulating tape is provided on an electrode tab-fixed region in the non-coating portions formed on both ends of the electrode plate, an internal short circuit may occur due to non-coating portion/non coating portion contact or non-coating portion/active material layer contact between electrode plates of opposite polarities, when damage or shrinkage of a separator occurs due to internal or external impact or heat generation.
Further, the non-coating portion without provision of the electrode tab is more highly susceptible to the occurrence of an internal short circuit, due to probable contact with the non-coating portion or active material layer of the electrode plate having an opposite polarity. Particularly when the non-coating portion of the electrode plate is in contact with the active material layer of the electrode plate having an opposite polarity, it may cause fatal damage to thereby result in the danger of ignition or explosion of the battery.